Volume of the cuboid = 720 cm³

Height of the cuboid = Volume of the cuboid / Base area of the cuboid
= 720 / 72 = 10 cm [By Hit Trail]

Surface area of the cuboid = 2 (lb + bh + hl)

Correct Option: A

Volume of the cuboid = 720 cm³

Height of the cuboid = Volume of the cuboid / Base area of the cuboid
= 720 / 72 = 10 cm [By Hit Trail]

Surface area of the cuboid = 2 (lb + bh + hl)
= 2(9 x 8 + 8 x 10 + 10 x 9 )
= 2 (72 + 80 + 90)
= 2 x 242
= 484 cm²

∴ It is obvious that length, breadth and height of the cuboid is 9 cm, 8 cm and 10 cm.

Let the edge of a square be x. and sum of its edges = 12 x
Now, by condition, x³ = 12x
⇒ x(x² - 12) = 0
⇒ Its total surface area = 6x²

Correct Option: C

Let the edge of a square be x. and sum of its edges = 12 x
Now, by condition, x³ = 12x
⇒ x(x² - 12) = 0
⇒ Its total surface area = 6x² = 6(12) = 72 sq units

Here, x = y = -19%
According to the formula,
Percentage decrease in surface area
= [x + y + xy/100]%

Correct Option: D

Here, x = y = -19%
According to the formula,
Percentage decrease in surface area
= [x + y + xy/100]%
= [- 19 - 19 + (-19) x (-19) /100]%
=[-38 + 361/100]%
= [-38 + 3.61]% = -34.39 %

Here, k = 12%
According to the formula,
Percentage increase in volume = [(1 + k/100)³ - 1] x 100%

Correct Option: A

Here, k = 12%
According to the formula,
Percentage increase in volume = [(1 + k/100)³ - 1] x 100%
= [(1 + 12/100)³ - 1] x 100%
= [(1.12)³ - 1] x 100%
= 0.404928 x 100% = 40.4928%

Given, r = 7 cm, h = 80 cm
Volume = πr²h = (22/7) x 7 x 7 x 80

Correct Option: C

Given, r = 7 cm, h = 80 cm
Volume = πr²h = (22/7) x 7 x 7 x 80
= 12320 cm³